The present invention relates to a read head assembly for sensing recorded information from tracks on moving magnetic media, such as magnetic tape, floppy disks or removable rigid disks, and, more particularly, to a magnetoresistive read head assembly for reading information from tracks having different track widths.
Recent advances in the art of magnetic data storage have resulted in improved storage densities. Typically, such improved storage densities are achieved by use of higher track densities in which the recorded information is stored in tracks narrower than those used previously. While it is usually not necessary for magnetic data storage drives to be able to write both the newer, high track density formats and the older, low track density formats, it is often desirable, for devices employing removable storage media, to be able to read both high and low track density formats. This capability to read both high and low track density formats may be referred to as "downward read capability."
In prior art magnetoresistive read heads, the dimensions of the active portion of the magnetoresistor correspond to the width of the track to be read. Due to the fixed dimensions of the active portion of the heads, these prior art devices are unsuitable for reading more than a single, fixed track width. Although it is theoretically possible to read a wide track width with a narrow track width head, such an arrangement produces low output voltages and a greater probability of dropout-induced errors. The low output voltage associated with narrow track width magnetoresistive heads can be compensated by increasing the current; however, this creates other problems, particularly heating of the magnetoresistive element. In addition, high current densities can cause electromigration in the magnetoresistive element. Further, high currents can cause stray fields from the magnetoresistive element of sufficient strength to erase the signal stored in the lower density medium. For some applications, particularly multi-track tape, heating is the limiting factor on the amount of current applied to the magnetoresistive element.
Accordingly, there is a need in the art for a single magnetic recording head which avoids the above problems while having the capability of reading tracks of various widths to provide downward read capability.